1. Field of the Invention
The present invention relates to a grouping device for arranging input signals in groups, more particularly, to a grouping device disposed between a central processing unit (CPU) and a plurality of input-output units and grouping a plurality of interrupt requests output from the input-output units into a number of interrupt levels of the CPU.
2. Description of the Related Art
In the prior art, a grouping device for arranging input signals in groups is used, for example, as a interrupt controller disposed between a CPU and a plurality of input-output units, and groups a plurality of interrupt requests output from the input-output units into a number of interrupt levels of the CPU.
Generally, the total number of input-output units connected to the CPU is greater than the number of groups or channels of the CPU; for example, the total number of interrupt requests output from the input-output units is greater than the total number of interrupt levels of the CPU. Therefore, in a data processing system, the interrupt requests output from the input-output units must be formed into groups corresponding to the interrupt levels of the CPU on the basis of whether or not the same relationship, for example, they have the same processing speed, exists between each interrupt request and each interrupt level.
Note, the total number of input-output units is not constant and is subject to change. Therefore, the relationships used to group the interrupt requests into the interrupt levels are registered in an erasable type register table, and thus, when the interrupt requests are grouped into the interrupt levels, the interrupt requests are grouped by referring to the register table.
In the conventional grouping device, the register table comprises n registers corresponding to the total number n of interrupt requests or input-output units. In this case, each register comprises an m-bits data storing portion corresponding to the total number m of the interrupt levels of the CPU. As described above, the number n of input-output units is greater than the total number m of the interrupt levels of the CPU, and consequently, in the conventional grouping device, one register must be provided for each input-output unit, and thus the total number of the registers is high, the register access time is long, and confirmation by the CPU of the relationships stored in the register table is difficult.